Mistflower

Mistflower (Eupatorium coelestinum) or Blue Boneset is a late summer to fall-blooming herbaceous perennial. It looks like annual ageratum and in that regard is sometimes commonly called hardy ageratum. But it is perennial and can spread aggressively by rhizomes. It typically grows to 1-2 feet tall on downy purplish stems clad with coarsely-toothed, ovate-deltoid leaves. The flowers of this member of the aster family lack rays. Numerous small, fluffy, tubular, blue-purple flowers with discoid heads bloom from July to October in dense flat topped terminal clusters (corymbs).

The blooming period occurs from mid-summer to early autumn, lasting about 1-2 months. Afterwards, the florets are replaced by achenes with small tufts of hair; they are distributed by the wind. The root system is highly rhizomatous; this plant readily forms colonies.

Habitats include river-bottom prairies, moist open woodlands, gravelly seeps, borders of lakes and rivers, moist meadows in wooded areas, bases of bluffs, and ditches. This plant usually occurs in poorly drained areas and near sources of water.

Easily grown in average, medium to wet, well-drained soils in full sun to part shade. Prefers moist, fertile, humusy soils which do not dry out. Mistflower is a vigorous plant that spreads aggressively by rhizomes and self-seeding. Propagate by clump division in early spring. Plants will grow in wet areas. Taller plants may be cut back in summer to prevent flopping.